In recent years, in order to improve the fuel consumption of automobiles, hybrid cars, in which internal combustion engines and motors are used in combination, have been quickly gaining in popularity. On the other hand, the commercialization of electric cars, which can run by motors alone, has been progressing. In order to realize these vehicles, a power converter for converting DC power to AC power and converting AC power to DC power needs to be provided between a battery and a motor.
In the field of hybrid cars and electric cars, there is a demand for reduction in size and high reliability of semiconductor power converters. In order to realize the reduction in size and high reliability of the semiconductor power converter, a semiconductor power converter with high cooling efficiency is needed. As a method for realizing this, there has been proposed a double-surface radiation type semiconductor device in which conductors are connected to front and back surfaces of a semiconductor element and heat is dissipated to a radiator from the conductors.